a. Field of the Invention
The instant disclosure relates to medical ablation procedures, including detection and prevention of adverse events during cardiac ablation.
b. Background Art
During ablation procedures such as, for example, cardiac ablation procedures, it may be desirable to avoid or minimize adverse events that can result in damage to the tissue being ablated, such as charring of the tissue, localized coagulation, tamponade, effusion, steam pop, and tissue pop. Many of these adverse events can occur as a result of excessive energy delivery to an ablation site. Thus, it is generally desirable to monitor an ablation site for indications of adverse events during the provision of energy and reduce or interrupt the provision of energy if an adverse event is imminent.
Temperature and impedance are known inputs that can be evaluated for predicting, preventing, and diagnosing adverse events. For example, the local temperature at an ablation site (e.g., the temperature of an ablation electrode) can be monitored with a temperature sensor in or near the distal tip of an ablation catheter, such as described in U.S. Pat. No. 7,857,810, hereby incorporated by reference in its entirety as though fully set forth herein. In response to temperature measurements, the ablation generator can be controlled to increase, reduce, or cease the provision of ablation energy. Alternatively or additionally, irrigation fluid can be controlled responsive to a sensed temperature, such as described, for example, in U.S. Patent Application Publication No. 2010/0168736, hereby incorporated by reference in its entirety as though fully set forth herein. A high temperature may indicate a possible adverse event; however, accurately monitoring the temperature of several layers of tissue can be difficult.
Impedance also can be used for monitoring the condition of an ablation site for prediction and diagnosis of adverse events. For example, as discussed herein and described in U.S. Patent Application Publication No. 2011/0144657, which is hereby incorporated by reference in its entirety as though fully set forth herein, a complex impedance can be monitored for predicting endocardial barotrauma (sometimes referred to as “tissue pop”). Though impedance monitoring may provide a means for detecting adverse events, additional monitoring mechanisms and processes may be desirable to further increase the likelihood that an adverse event can be detected in advance and possibly prevented.